<!DOCTYPE html>
<html>
<head>
<title>Заголовок документа</title>
<style>
label {
margin-right: .5em;
position: relative;
top: 1px;
}
input[type="radio"]:indeterminate + label {
color: #8ebf42;
}
</style>
</head>
<body>
<h2>Пример селектора :indeterminate</h2>
<form>
<input type="radio" name="option" value="yes" id="yes">
<label for="yes">Yes</label>
<input type="radio" name="option" value="no" id="no">
<label for="no">No</label>
<input type="radio" name="option" value="don't know" id="don't-know">
<label for="don't-know">Don't know</label>
</form>
</body>
</html>